1. Field of the Invention
The present invention relates to localization systems. In particular, the present invention relates to systems for localizing an acoustic source based on both image information and audio information.
2. Description of the Prior Art
In most localization systems for localizing acoustic sources, microphone arrays are used to receive acoustic signals and the time delay of arrival (TDOA) algorithm is used for estimating the location of an acoustic source based on the time instants when the microphones receive acoustic signals. However, if there are obstacles blocked between the microphones and the acoustic source, the estimated result generated by this traditional method is usually inaccurate.
U.S. Pat. No. 6,826,284 discloses a localization method that utilizes TDOA and estimates the channel transfer function with the adaptive eigenvalue decomposition algorithm (AEDA) and least-mean square (LMS) algorithm. This method can solve the problem induced by obstacles but is useful only under circumstances with microphones matching with each other and without noises.
As known by those skilled in the art, plural microphones arranged in a single direction can only detect the location of an acoustic source relative to the microphone array in this particular direction. In the localization method disclosed in U.S. Pat. No. 6,243,471, plural microphone groups are used for receiving the acoustic signal generated by an acoustic source. Each of the groups includes at least three microphones. The three-dimensional location of the acoustic source is estimated based on the received signals and the geometric relationships of the microphone groups. Although this method can find out the three-dimensional location of the acoustic source and solve the problem induced by obstacles, a large number of microphones are needed and the system architecture is considerably complicated. Besides, noises may induce errors easily and the microphones are also required to match with each other.
In U.S. Pat. No. 6,449,593, a beamformer for generating beams at specific angles is utilized to suppress noises when the microphones are detecting acoustic signals. This method can be performed under circumstances with noises. However, the problem induced by obstacles cannot be solved and the microphones are required to match with each other, too.
U.S. patent application 2004/00132752 discloses a localization method that estimates the location of an acoustic source with a covariance matrix. The effect of noises can be minimized only when the noises have a Gaussian distribution and an average value equal to zero. Moreover, this method cannot solve the problem induced by obstacles and the microphones are also required to match with each other.
U.S. Pat. No. 5,778,082 discloses a method that eliminates the effect of noises by subtracting the cross-correlation matrix of noises from the cross-correlation matrix of acoustic signals. The disadvantage of this method is that if the cross-correlation matrix of noises is not correctly estimated, the location of the acoustic source cannot be localized correctly, either. Besides, this method cannot solve the problem induced by obstacles and the microphones are also required to match with each other.
As described above, in prior arts, there is not a solution that can solve all the aforementioned problems and estimate the three-dimensional location of an acoustic source.